There are presently numerous portable devices from which and to which data is to be transmitted by wireless means. One possibility which suggests itself here is to realize the data transmission by electromagnetic coupling. In doing this, particular difficulties arise if the devices used are very small, because in such a situation there are problems in integrating an antenna structure into the device concerned. An important example of a very small device for which wireless data transmission is required is a hearing aid.
In accordance with the prior art, the transmission of data to a hearing aid is often realized in practice by inductive transmission links. For this purpose, an induction loop is integrated into the hearing aid. However, this type of inductive transmission of speech or data, as applicable, to a hearing aid requires special installations in the area concerned, where the wireless transmission of speech or data is to take place.
In another form of embodiment of wireless radio transmission systems, magnetic antennas are used in the hearing aids. These essentially couple into the magnetic components of an electromagnetic field, and are generally designed as conductive loops. Radio transmission systems of this type generally work at frequencies which are significantly lower than the frequencies used in mobile radiocommunications, e.g. in the VHF band at 174 MHz.
European patent application EP 1 326 302 A2 describes a fractal antenna structure which is realized on an integrated circuit, and which can be used in a hearing aid. However, the fractal antennas described in the document cited can only be considered for significantly higher frequencies.